Abstract: Single point gap discharge, single point contact discharge and continuous discharge with rotary electrode tests were conducted in order to study the discharge mechanism of electro-spark deposition with rotary electrode. The voltage and current waveform between the electrode and substrate in discharge process were collected and analyzed. The results show that the medium between electrode and substrate can be broken down and result in gap discharge under certain voltage and gap conditions. Contact discharge mainly consists of two stages: short circuit discharge and gap discharge. The contact state between electrode and substrate is complicated and variable in the process of electro-spark deposition with rotary electrode. During the discharge process, there exists not only non-contact discharge phenomena, but contact discharge and short circuit discharge phenomena. Most of them are contact discharge phenomena.